What is the secret of the old castle on the hill, and why are the locals so afraid of it? When flashing lights are seen in a distant tower, Philip, Dinah, Lucy-Ann, and Jack decide to investigate—and discover a very sinister plot concealed within its hidden rooms and gloomy underground passages. Paperback , 288 pages Published March 1st 2006 by Pan Macmillan (first published 1946)